Crystal growing systems and crucibles for enhancing heat transfer to a melt

ABSTRACT

A system for growing an ingot from a melt includes an outer crucible, an inner crucible, and a weir. The outer crucible includes a first sidewall and a first base. The first sidewall and the first base define an outer cavity for containing the melt. The inner crucible is located within the outer cavity, and has a central longitudinal axis. The inner crucible includes a second sidewall and a second base having an opening therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/087,604, filed Nov. 22, 2013, which is incorporated herein byreference in its entirety.

FIELD

The field of the disclosure relates generally to systems for producingingots of semiconductor or solar material from a melt and, moreparticularly, to systems for reducing dislocations and impurityconcentrations in the ingot, and enhancing heat transfer within themelt.

BACKGROUND

In the production of single silicon crystals grown by the Czochralski(CZ) method, polycrystalline silicon is first melted within a crucible,such as a quartz crucible, of a crystal pulling device to form a siliconmelt. The puller then lowers a seed crystal into the melt and slowlyraises the seed crystal out of the melt. To produce a single, highquality crystal using this method, the temperature and the stability ofthe surface of the melt immediately adjacent to the ingot must bemaintained substantially constant. Further, the melt temperatureadjacent to the ingot must be maintained at a sufficiently hightemperature to prevent the melt from prematurely solidifying. Priorsystems for accomplishing this goal have not been completelysatisfactory. Thus, there exists a need for a system that not onlylimits temperature fluctuations and surface disruptions in the meltimmediately adjacent to the ingot, but also provides sufficient heattransfer to the melt adjacent to the ingot for maintaining thetemperature of the melt.

This Background section is intended to introduce the reader to variousaspects of art that may be related to various aspects of the presentdisclosure, which are described and/or claimed below. This discussion isbelieved to be helpful in providing the reader with backgroundinformation to facilitate a better understanding of the various aspectsof the present disclosure. Accordingly, it should be understood thatthese statements are to be read in this light, and not as admissions ofprior art.

BRIEF SUMMARY

A first aspect of the present disclosure is a system for growing aningot from a melt. The system includes an outer crucible, an innercrucible, and a weir. The outer crucible includes a first sidewall and afirst base. The first sidewall and the first base define an outer cavityfor containing the melt. The inner crucible is located within the outercavity, and has a central longitudinal axis. The inner crucible includesa second sidewall and a second base having an opening therein. Theopening in the second base is concentric with the central longitudinalaxis. The weir is disposed between the outer crucible and the innercrucible for supporting the inner crucible.

Another aspect of the present disclosure is a system for growing aningot from a melt. The system includes an outer crucible, an innercrucible, and a weir. The outer crucible includes a first sidewall and afirst base. The first sidewall and the first base define an outer cavityfor containing the melt. The inner crucible is located within the outercavity, and includes a second sidewall and a second base having anopening therein. The opening has a first cross-sectional area. The weiris disposed between the outer crucible and the inner crucible forsupporting the inner crucible. The weir has a second cross-sectionalarea. The ratio between the first cross-sectional area and the secondcross-sectional is at least about 0.25.

Another aspect of the present disclosure is a system for growing aningot from a melt. The system includes an outer crucible, an innercrucible, a first weir, and a second weir. The outer crucible includes afirst sidewall and a first base. The first sidewall and the first basedefine an outer cavity for containing the melt. The inner crucible islocated within the outer cavity, and includes a second sidewall and asecond base having an opening therein. The second sidewall and thesecond base define an inner cavity. The opening is sized to facilitatethe transfer of heat between the outer cavity and the inner cavity. Thefirst weir is disposed between the outer crucible and the innercrucible. The second weir is positioned radially outward from the firstweir for separating the melt into multiple melt zones.

Various refinements exist of the features noted in relation to theabove-mentioned aspects. Further features may also be incorporated inthe above-mentioned aspects as well. These refinements and additionalfeatures may exist individually or in any combination. For instance,various features discussed below in relation to any of the illustratedembodiments may be incorporated into any of the above-described aspects,alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is cross-section of a crystal growing system including a crucibleassembly;

FIG. 2 is an enlarged cross-section of the crucible assembly of FIG. 1;

FIG. 3 is an exploded view of a plurality of weirs used in the crucibleassembly of FIG. 2;

FIG. 4 is a side elevation of the plurality of weirs of FIG. 3 in anassembled configuration;

FIG. 5 is a cross-section of the plurality of weirs of FIGS. 3-5 takenalong line 5-5 of FIG. 4;

FIG. 6 is a partial cross-section of the plurality of weirs of FIGS. 3-5taken along line 6-6 of FIG. 5;

FIG. 7 is a top perspective of a second crucible used in the crucibleassembly of FIG. 2;

FIG. 8 is a top elevation of the second crucible of FIG. 7;

FIG. 9 is a cross-section of the second crucible of FIGS. 7-8 takenalong line 9-9 of FIG. 8; and

FIG. 10 is a partial cross-section of the crystal growing system of FIG.1 illustrating the temperature field and streamlines of a melt.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION

In a crystal growing system using a continuous Czochralski process, oneor more silica weirs are located between an outer or first crucible andan inner or second crucible to form a crucible assembly. The secondcrucible may be supported by the one or more weir(s) that are submergedwithin the melt. These weir(s) create multiple zones within the crucibleassembly to limit the melt within one zone from passing into anotherzone to specific locations. One example of such a crystal growing systemis disclosed in U.S. patent application Ser. No. 13/804,585 (the “'585Application”) filed Mar. 14, 2013, the entirety of which is herebyincorporated by reference.

Referring to FIG. 1, a crystal growing system is shown schematically andis indicated generally at 100. The crystal growing system 100 is used toproduce a single crystal ingot by a Czochralski method. As discussedherein, the system is described in relation to the continuousCzochralski method of producing single crystal ingots, though a batchprocess may be used. For example, the process may be used in a“recharge” CZ process.

The crystal growing system 100 includes a susceptor 150 supported by arotatable shaft 152, and a crucible assembly 200 that contains a siliconmelt 112 from which an ingot 114 is being pulled by a puller 134. Duringthe crystal pulling process, a seed crystal 132 is lowered by the puller134 into the melt 112 and then slowly raised from the melt 112. As theseed crystal 132 is slowly raised from the melt 112, silicon atoms fromthe melt 112 align themselves with and attach to the seed crystal 132 toform the ingot 114.

The system 100 also includes a feed system 115 for feeding solidfeedstock material 116 into the crucible assembly 200 and/or the melt112, a heat reflector 160, and a heat system 123 for providing heat tothe crucible assembly 200 and maintaining the melt 112.

With additional reference to FIG. 2, the crucible assembly 200 includesa first crucible 210 having a first base 212 and a first sidewall 214, asecond crucible 230 having a second base 232 and a second sidewall 234,and a plurality of concentrically arranged weirs 260, 280, 300.

The first base 212 has a top surface 218 and the second base 232 has abottom surface 238 and a top surface 240. Each sidewall 214, 234 extendsaround the circumference of the respective base 212, 232, and defines adiameter 220, 242 of the respective crucible 210, 230. The firstsidewall 214 and the first base 212 form an outer cavity 216. The secondsidewall 234 and the second base 232 form an inner cavity 236. Thesecond crucible 230 is sized and shaped to allow placement of the secondcrucible 230 within the outer cavity 216 of the first crucible 210. Insome embodiments, the first crucible may have an internal diameter ofabout 32 inches and the second crucible may have an internal diameter ofabout 24 inches. In other embodiments, the first crucible may have aninternal diameter of about 24 inches and the second crucible may have aninternal diameter of about 16 inches. In yet other embodiments, thefirst and second crucibles may have any suitable internal diameter thatenables the crucible assembly 200 to function as described herein.

With additional reference to FIGS. 3-6, the plurality of concentricallyarranged weirs includes a first weir 260, a second weir 280, and a thirdweir 300. While the illustrated embodiment is shown and described asincluding three weirs, the system 100 may include more or fewer thanthree weirs, such as one weir, two weirs, or any other suitable numberof weirs that enables the system 100 to function as described herein.

The weirs 260, 280, 300 each have a cylindrical body with an open topand bottom. Each weir 260, 280, 300 also has a top weir surface 262,282, 302 and a bottom weir surface 264, 284, 304, respectively.

The weirs 260, 280, 300 support the second crucible 230 within the outercavity 216. More specifically, the bottom weir surfaces 264, 284, 304rest against the top surface 218 of first base 212, and the bottomsurface 238 of the second base 232 rests against the top weir surfaces262, 282, 302. In the illustrated embodiment, each bottom weir surface264, 284, 304 is shaped to conform to a respective contact point of thefirst crucible 210. Similarly, each top weir surface 262, 282, 302 isshaped to conform to a respective contact point of the second crucible230. In alternative embodiments, one or more of the top and bottom weirsurfaces may have a shape other than a shape that conforms to arespective contact point of the first or second crucible.

Each weir 260, 280, 300 has a respective diameter 266, 286, 306 (FIG. 5)defined by the cylindrical body of the weir. In the illustratedembodiment, the diameter 306 of the third weir 300 is greater than thediameter 286 of the second weir 280, and the diameter 286 of the secondweir 280 is greater than the diameter 266 of the first weir 260. Theweirs 260, 280, 300 are concentrically aligned with one another suchthat the third weir 300 is positioned radially outward from the secondweir 280, and the second weir 280 is positioned radially outward fromthe first weir 260.

In some embodiments, one or more of the weirs 260, 280, 300 are bondedto the first base 212. In other embodiments, one or more the weirs 260,280, 300 are bonded to the second base 232, while in others, one or moreof the weirs 260, 280, 300 are bonded to both the first and second bases212, 232. The first crucible 210 and the second crucible 230 may be firepolished to improve the bond, e.g., the durability and reliability ofthe bond.

The weirs 260, 280, 300 and the second crucible 230 are arranged withinthe outer cavity 216 to separate the melt 112 into a plurality of meltzones. More specifically, the second crucible 230 and the weirs 260,280, 300 separate the melt 112 into an outer melt zone 170 and an innermelt zone 172 (FIG. 1). In the illustrated embodiment, the outer meltzone 170 is formed between the first sidewall 214 and the secondsidewall 234, and the inner melt zone 172 is formed within the innercavity 236 of the second crucible 230.

Each weir 260, 280, 300 is disposed between the first crucible 210 andthe second crucible 230, and is located along the first base 212 at alocation inward from the first sidewall 214 to inhibit movement of themelt 112 from the outer melt zone 170 to the inner melt zone 172. In theillustrated embodiment, the weirs 260, 280, 300 are arranged to furtherseparate the melt 112 into a first intermediate melt zone 174 (FIG. 1),formed between the third weir 300 and the second weir 280, and a secondintermediate melt zone 176 (FIG. 1), formed between the second weir 280and the first weir 260.

Each weir 260, 280, 300 includes at least one weir passageway 268, 288,308, respectively, extending therethrough to permit the melt to flowbetween the outer melt zone 170 and the inner melt zone 172. The weirpassageways 268, 288, 308 may be positioned along the respective weir260, 280, 300 to increase the path of travel for the melt 112 betweenthe outer melt zone 170 and the inner melt zone 172. In the illustratedembodiment, the weir passageways of adjacent weirs are diametricallyopposed from one another to provide a circuitous path for the melt 112between the outer melt zone 170 and the inner melt zone 172, although inother embodiments the weir passageways may be positioned at any suitablelocation along the respective weir. In the illustrated embodiment, eachweir 260, 280, 300 includes two weir passageways 268, 288, 308, althoughthe weirs may include more or fewer than two weir passageways, such asone passageway, three passageways, or any other suitable number ofpassageways that enables the system 100 to function as described herein.

In other embodiments, one or more weirs do not include passageways. Inthese embodiments, movement of the melt 112 from the outer melt zone 170to the inner melt zone 172 is limited to movement above or below theweirs.

With further reference to FIG. 1, the feed system 115 includes a feeder118 and a feed tube 120. Solid feedstock material 116 may be placed intothe outer melt zone 170 from feeder 118 through feed tube 120. Theamount of feedstock material 116 added to the melt 112 may be controlledby a controller 122 based on a temperature reduction in the meltresulting from the cooler feedstock material 116 being added to melt112.

As solid feedstock material 116 is added to melt 112, the surface of themelt may be disturbed where the solid feedstock material 116 isintroduced. This disturbance, if allowed to propagate through the melt112, also affects the ability of the silicon atoms of the melt 112 toproperly align with the silicon atoms of the seed crystal 132. The weirs260, 280, 300 and the second sidewall 234 of the second crucible 230inhibit inward propagation of the disturbances in the melt 112.

The heat reflector 160 is positioned adjacent the crucible assembly 200,and covers a portion of the inner cavity 236 and all of the outer cavity216. The heat reflector 160 inhibits line-of-sight polysiliconprojectiles from reaching the inner melt zone 172 during the addition ofthe solid feedstock material 116, and prevents gas from the outer meltzone 170 from entering the inner melt zone 172. The heat reflector 160also shields the ingot 114 from radiant heat from the melt 112 to allowthe ingot 114 to solidify.

The heat system 123 provides heat to crucible assembly 200 by heaters124, 126, and 128 arranged at suitable positions about the crucibleassembly 200. Heat from heaters 124, 126, and 128 initially melt thesolid feedstock material 116 and then maintains melt 112 in a liquefiedstate. Heater 124 is generally cylindrical in shape and provides heat tothe sides of the crucible assembly 200, and heaters 126 and 128 provideheat to the bottom of the crucible assembly. In some embodiments,heaters 126 and 128 are generally annular in shape, and are positionedaround and radially outward from the shaft 152.

Heaters 124, 126, and 128 are resistive heaters coupled to controller122, which controllably applies electric current to the heaters to altertheir temperature. A sensor 130, such as a pyrometer or like temperaturesensor, provides a continuous measurement of the temperature of melt 112at the crystal/melt interface of the growing single crystal ingot 114.Sensor 130 also may be directed to measure the temperature of thegrowing ingot. Sensor 130 is communicatively coupled with controller122. Additional temperature sensors may be used to measure and providetemperature feedback to the controller with respect to points that arecritical to the growing ingot. While a single communication lead isshown for clarity, one or more temperature sensor(s) may be linked tothe controller by multiple leads or a wireless connection, such as by aninfra-red data link or another suitable means.

The amount of current supplied to each of the heaters 124, 126, and 128by controller 122 may be separately and independently selected tooptimize the thermal characteristics of melt 112. In some embodiments,one or more heaters may be disposed around the crucible to provide heat.

As described above, the weirs and the second crucible separate the meltinto multiple melt zones. Separating the melt into multiple melt zonesand inhibiting the melt movement between the various zones facilitatesheating and melting silicon material (e.g., silicon feedstock) added inthe outer melt zone as the silicon material passes through the multiplezones to the inner melt zone, and thus prevents un-liquefied feedstockmaterial from passing into the inner melt zone and disturbing thestructural integrity of the ingot being formed therefrom.

Further, inhibiting movement of the melt between the zones allows thesurface of the inner zone to remain relatively undisturbed. The weirsand the second crucible substantially prevent disturbances in the outermelt zone or intermediate melt zones from disrupting the surface of themelt in the inner melt zone by substantially containing the energy wavesproduced by the disturbances in the outer melt zone and intermediatemelt zones.

The transfer of heat to the inner melt zone may, however, be adverselyaffected by the addition of too many weirs. For example, quartz weirscan act as a thermal barrier to heat provided by heaters 124, 126, 128,which may prevent a sufficient amount of heat from being transferred tothe inner melt zone 172 to maintain the liquid melt 112. The secondcrucible 230 is therefore configured to facilitate the transfer of heatto the inner melt zone 172.

More specifically, with additional reference to FIGS. 7-9, the secondbase 232 of the second crucible 230 has an opening 244 defined by anannular rim 246 extending from the top surface 240 of the second base232 to the bottom surface 238 of the second base 232. While theillustrated embodiment is shown and described as including one opening,alternative embodiments may have more than one opening formed in thesecond crucible 230.

The rim 246 is substantially parallel to the second sidewall 234 of thesecond crucible, although the rim 246 may be tapered inward or outwardwith respect to a central longitudinal axis 248 of the second crucible230.

The opening 244 extends through the second crucible 230, and is sizedand shaped to facilitate the transfer of heat from the outer cavity 216to the inner cavity 236. More specifically, the opening is sized basedon the size of the first weir 260. In one suitable embodiment, forexample, the opening has a diameter 250 that is sized based on thediameter 266 of the first weir 260. More specifically, the ratio betweenthe diameter 250 of the opening 244 and the diameter 266 of the firstweir 260 is at least about 0.5, more suitably at least about 0.7, and,even more suitably, at least about 0.95. In the illustrated embodiment,for example, the ratio between the diameter 250 of the opening 244 andthe diameter 266 of the first weir 260 is about 1.0.

In another suitable embodiment, the opening 244 is sized based on across-sectional area enclosed by the first weir 260 taken perpendicularto the central longitudinal axis 248 of the second crucible 230. In onesuitable embodiment, for example, the ratio between the cross-sectionalarea of the opening 244 and the cross-sectional area of the first weir260 is at least about 0.25, more suitably at least about 0.5, and evenmore suitably, at least about 0.8. In the illustrated embodiment, forexample, the ratio between the cross-sectional area of the opening 244and the cross-sectional area of the first weir 260 is about 1.0.

In the illustrated embodiment, the opening 244 has a substantiallycircular shape, although in other embodiments, the opening may have anysuitable shape that enables the system 100 to function as describedherein.

The opening 244 is positioned radially inward from the innermost weir(i.e., the first weir 260) such that separation between the multiplemelt zones is maintained. In the illustrated embodiment, the opening 244is concentric with the central longitudinal axis 248 of the secondcrucible 230, although the opening 244 may be offset from the centrallongitudinal axis 248 of the second crucible 230. Also, in theillustrated embodiment, the opening 244 is sized and positioned suchthat the rim 246 is substantially aligned with the radially inner wallof the first weir 260.

The opening 244 also provides fluid communication between the outer meltzone 170 and the inner melt zone 172, and allows the melt 112 to flowbetween the inner cavity 236 and the outer cavity 216.

The opening 244 enables heat to be transferred directly from the firstcrucible 210 to the inner melt zone 172. Further, the temperaturegradient across the melt 112 from the first base 212 of the firstcrucible 210 to the surface of the melt 112 causes the melt 112 torecirculate within the inner melt zone 172, thereby enhancing thetransfer of heat from the first crucible 210 to the melt 112 within theinner melt zone 172.

Specifically, referring to FIG. 10, streamlines and temperature fieldsof the melt 112 are shown within the inner melt zone 172. The melt 112is hotter near the first base 212 of the first crucible 210 and thefirst weir 260 than it is near the surface of the melt 112. As a result,the melt 112 recirculates between the hotter and cooler portions,thereby enhancing the transfer of heat from the first crucible 210 tothe melt 112 within the inner melt zone 172. Further, recirculation ofthe melt 112 within the inner melt zone 172 provides a more uniformdistribution of impurities within the melt 112 (e.g., by carrying highconcentrations of impurities away from the ingot-melt interface),thereby reducing the level of impurity concentrations within the melt112 and enhancing the quality of the ingot 114 grown from the melt 112.

As described above, the crystal growing systems of the presentdisclosure provide an improvement over known crystal growing systems.The crystal growing systems of the present disclosure enable separationof a silicon melt into multiple melt zones, while at the same timeenhancing heat transfer to an inner melt zone of the melt.

Separating the melt into multiple melt zones and inhibiting the meltmovement between the various zones facilitates heating and meltingsilicon material (e.g., silicon feedstock) added in the outer melt zoneas the silicon material passes through the multiple zones to the innermelt zone, and thus prevents un-liquefied feedstock material frompassing into the inner melt zone and disturbing the structural integrityof the ingot being formed therefrom. Further, inhibiting movement of themelt between the zones allows the surface of the inner zone to remainrelatively undisturbed. The weirs and the second crucible substantiallyprevent disturbances in the outer melt zones or intermediate melt zonesfrom disrupting the surface of the melt in the inner melt zone bysubstantially containing the surface vibrations produced by thedisturbances in the outer melt zone and intermediate melt zones.

Embodiments of this disclosure may also reduce the amount of oxygen inthe ingot, lower the consumption rates of the weir and second crucibleproviding a longer run life, and provide better system performance, asdescribed in the co-pending '585 Application.

Another benefit is that the volume and liquid-quartz surface area of theouter melt zone is increased compared to known crystal growing systems.The increase in volume and liquid-quartz surface area of the outer meltzone enhances heat transfer to the outer melt zone increasing the ratethat solid feedstock material is liquefied. The increase in theconversion rate is particularly beneficial when the rate of adding solidfeedstock material is high and a large amount of heat is needed tocontinuously liquefy solid feedstock material.

The above embodiments also provide improved impurity characteristicswhile reducing incidents of loss of crystal structure due to solidparticles impacting the crystal.

Additionally, the above embodiments enhance the transfer of heat to aninner melt zone of the melt. Enhancing the transfer of heat to the innermelt zone substantially prevents the melt from solidifying within theinner melt at locations other than the melt-ingot interface.Additionally, enhancing the transfer of heat to the inner melt zonecauses the melt to recirculate within the inner melt zone, therebyfurther enhancing the transfer of heat to the inner melt zone andproviding a more uniform distribution of impurities within the melt.

When introducing elements of the present invention or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A system for growing an ingot from a melt, thesystem comprising: an outer crucible defining an outer cavity forcontaining the melt; an inner crucible located within the outer cavity,the inner crucible having a central longitudinal axis, the innercrucible including a second sidewall and a second base extendingradially inward from the second sidewall and having an opening therein,the opening in the second base, the second crucible, and the outercrucible concentric with the central longitudinal axis; and a first,annular weir separating the outer crucible from the inner crucible, thefirst weir separate from the inner crucible and the outer crucible. 2.The system of claim 1, wherein the opening has a first diameter, thefirst weir has a second diameter, the second sidewall has a thirddiameter, the third diameter being greater than the first and seconddiameters.
 3. The system of claim 1, wherein the opening is defined byan annular rim tapered with respect to the central longitudinal axis,the rim being substantially aligned with the first weir.
 4. The systemof claim 1, wherein the first weir has a plurality of first weirpassageways extending therethrough to permit the melt to flow between anouter melt zone and an inner melt zone.
 5. The system of claim 4,further comprising a second, annular weir positioned radially outwardfrom the first weir and supporting the inner crucible along the secondbase, the second weir having a plurality of second weir passagewaysextending therethrough.
 6. The system of claim 5, wherein the first weirpassageways and the second weir passageways are diametrically opposedfrom one another to provide a circuitous path for the melt.
 7. Thesystem of claim 1, further comprising a shaft for supporting the innerand outer crucibles, and a heater disposed radially outward from theshaft.
 8. The system of claim 1, further comprising a heater disposedbelow the first base of the outer crucible and radially inward from thefirst sidewall of the outer crucible.
 9. A system for growing an ingotfrom a melt, the system comprising: an outer crucible defining an outercavity for containing the melt; an inner crucible located within theouter cavity, the inner crucible including a second sidewall and asecond base extending radially inward from the second sidewall andhaving an opening therein, the opening having a first cross-sectionalarea; a first, annular weir separating the outer crucible from the innercrucible, the first weir having a second cross-sectional area, wherein aratio between the first cross-sectional area and the secondcross-sectional is at least about 0.25, the first weir being separatefrom the inner crucible and the outer crucible; and a heat reflectordisposed on top of the inner and outer crucibles, the heat reflectorconfigured to prevent a flow of gas from the outer crucible to the innercrucible.
 10. The system of claim 9, wherein the second sidewall and thesecond base define an inner cavity, the opening in the second base sizedto facilitate heat transfer from the outer cavity to the inner cavity.11. The system of claim 9, wherein the opening has a first diameter, thefirst weir has a second diameter, and the ratio between the firstdiameter and the second diameter is at least about 0.5.
 12. The systemof claim 11, wherein the first weir has a first weir passagewayextending therethrough to permit the melt to flow between an outer meltzone and an inner melt zone.
 13. The system of claim 12, furthercomprising a second, annular weir positioned radially outward from thefirst weir, the second weir having a second weir passageway extendingtherethrough.
 14. The system of claim 13, wherein the first weirpassageway and the second weir passageway are diametrically opposed fromone another to provide a circuitous path for the melt.
 15. The system ofclaim 11, further comprising a shaft for supporting the inner and outercrucibles, and a heater disposed radially outward from the shaft.
 16. Asystem for growing an ingot from a melt, the system comprising: an outercrucible; an inner crucible located within the outer crucible, the innercrucible including a second sidewall and a second base extendingradially inward from the second sidewall and having an opening therein,the opening has a first diameter and the second sidewall has a thirddiameter; a first, annular weir separate from the inner crucible and theouter crucible, the first weir has a second diameter less than the thirddiameter and greater than the first diameter; and a second, annular weirseparate from the inner crucible and the outer crucible and having afourth diameter less than the third diameter and greater than the seconddiameter, at least one of the first weir or second weir separating theouter crucible from the inner crucible.
 17. The system of claim 16further comprising a third, annular weir separate from the innercrucible and the outer crucible and having a fifth diameter less thanthe third diameter and greater than the third diameter.
 18. The systemof claim 17, wherein the inner crucible has a central longitudinal axis,and the opening in the second base, the inner crucible, the outercrucible, the first weir, the second weir, and the third weir areconcentric with the central longitudinal axis.
 19. The system of claim16, wherein the ratio between the first diameter and the second diameteris at least about 0.5.
 20. The system of claim 17, wherein the firstweir has a first weir passageway extending therethrough, the second weirhas a second weir passageway extending therethrough, the third weir hasa third weir passageway extending therethrough, at least two of thefirst weir passageway, the second weir passageway, and the third weirpassageway being diametrically opposed from one another.